Tissue treatment

ABSTRACT

A method of treating tissue includes placing substantially spherical polymer particles in the tissue. The particles include an interior region having relatively large pores and a first region substantially surrounding the interior having fewer relatively large pores than the interior region.

CLAIM OF PRIORITY

This application is a continuation-in-part application of and claimspriority to U.S. patent application Ser. No. 10/215,594, entitled“Embolization” and filed on Aug. 9, 2002, which is acontinuation-in-part of U.S. Ser. No. 10/109,966, filed Mar. 29, 2002.This application also claims priority to U.S. patent application Ser.No. 60/388,446, entitled “Bulking Agents” and filed on Jun. 12, 2002.The entire contents of both applications are hereby incorporated byreference.

TECHNICAL FIELD

This invention relates to the treatment of tissue, such as theintroduction of particles into body tissue for repair and/oraugmentation.

BACKGROUND

The body includes various passageways through which bodily matter orfluids, such as urine, can flow. The flow of material through thepassageways is in part affected by tissue surrounding the passageways.For example, the tissue can constrict and cause a passageway to narrowor to close, thereby restricting flow of material through thepassageway.

In some disorders, the tissue can no longer affect a passageway. Forexample, while urine normally flows down in one direction from thekidneys, through tubes called ureters, and to the bladder, invesicoureteral reflux (VUR), urine can flow abnormally from the bladderback into the ureters. In gastroesophageal reflux disease (GERD),sometimes called “reflux”, acid from the stomach can flow back into theswallowing tube, or esophagus. Other disorders include, for example,urinary incontinence, i.e., loss of urinary control, and fecalincontinence.

One method of treating such disorders includes placing, e.g., injecting,a bulking material in the tissue adjacent to the passageway. The bulkingmaterial can narrow the passageway and, by providing bulk, allows thetissue to constrict the passageway more easily.

SUMMARY

This invention relates to the treatment of tissue.

In one aspect, the invention features a method of treating tissueincluding placing substantially spherical polymer particles in thetissue. The particles have an interior region having relatively largepores and a first region substantially surrounding the interior regionhaving fewer relatively large pores than the interior region.

Embodiments may include one or more of the following features. Theparticles are injected into the tissue. The particles are injectedpercutaneously. The particles are delivered through a catheter. Themethod includes forming a cavity in the tissue, and placing theparticles in the cavity. The tissue is adjacent to a body passageway.The passageway is defined by a ureter. The tissue is adjacent to a bodypassageway, and the particles are placed in an amount effective tonarrow the passageway.

The particles can be polyvinyl alcohol. The polyvinyl alcohol can be 1,3diol acetalized. The particles can include a polysaccharide. Thepolysaccharide can include alginate.

The particles can include a therapeutic agent.

In another aspect, the invention features a method of treating anindividual. The method includes placing a therapeutically effectiveamount of substantially spherical particles including polyvinyl alcoholin a tissue of the individual. The particles have an interior regionhaving relatively large pores and a first region substantiallysurrounding the interior region having fewer relatively large pores thanthe interior region.

Embodiments can include one or more of the following features.

The method further includes selecting the individual diagnosed withgastroesophageal reflux disease. The tissue is adjacent to agastrointestinal tract. The method further includes selecting theindividual diagnosed with vesicoureteral reflux. The tissue is adjacentto a ureter.

The method can further include selecting an individual diagnosed withurinary incontinence, fecal incontinence, intrinsic sphinctericdeficiency, and/or vocal cord paralysis. The method can further includeselecting an individual in need of a reconstructive or cosmeticprocedure.

The particles can be placed percutaneously and/or through a catheter.

In another aspect, the invention features a method of delivering atherapeutically effective amount of substantially spherical polymerparticles. The particles include polyvinyl alcohol and include aninterior region having relatively large pores and a surface regionhaving fewer relatively large pores. The particles can have a diameterof about 1200 micron or less, a surface with a predominant pore size ofabout 2 micron or less and pores interior to surface of about 10 micronor more, and/or a surface region from about 0.8r to r, the predominantpore size in the surface region being smaller than the predominant poresize in a region C to 0.3r.

Embodiments may also include one or more of the following. Therelatively large pores are about 20 or 30 micron or more. The surfaceregion is about r to 0.8r. The surface region is about r to ⅔r. Theparticles include a body region from about ⅔r to r/3 includingintermediate size pores and the body region has more intermediate sizepores than the surface region. The center region is from about r/3 to C,the outer region including large size pores and the body region hasfewer large size pores than the center region. The intermediate sizepores are about 2 to 18 microns. The surface region is substantiallyfree of pores greater than about 5 micron.

Embodiments may also include one of the following. The predominant poresize progressively increases from surface to the center of the particle.The predominant pore size on the particle surface is about 1 micron orless. The particles have a surface region from about (2r)/3 to thesurface wherein the predominant pore size is in the range of about 1micron or less. The predominant pore size is about 0.1 micron or less.Interior of said surface region, the particles have a predominant poresize in the range of about 2 to 35 microns. The particles include acenter region from about r to r/3 in which the predominant pore size isabout 20 to 35 micron. The particles have a body region from r/3 to(2r)/3 in which the predominant pore size is about 2 to 18 micron. Theparticles have a surface region from about (2r)/3 to the periphery andthe predominant pore size in the surface region is about 10% or lessthan the predominant pore size in the interior to the surface region.The particles include a surface region from about 0.8r to r wherein thepredominant pore size is about 1 micron or less. The particles include aregion from about C to 0.8r includes pores having a diameter of 10microns or more. The region C to 0.8r has a predominant pore size ofabout 3.5 to 2 micron. The particles have a density of about 1.1 toabout 1.4 g/cm3. The particles have a density of about 1.2 to 1.3 g/cm³.The particles have a sphericity of about 90% or more. The particles havean initial sphericity of about 97% or more. The particles have asphericity of about 0.90 after compression to about 50%. The particleshave a size uniformity of about +15% or more.

Embodiments may also include one or more of the following. The particlesinclude about 1% or less polysaccharide. The polysaccharide is alginate.The alginate has a guluronic acid content of about 60% or greater. Theparticles are substantially insoluble in DMSO. The particles aresubstantially free of animal-derived compounds. The polyvinyl alcohol iscomposed of substantially unmodified polyvinyl alcohol prepolymer. Thepolyvinyl alcohol is predominantly intrachain 1,3-diols acetalized. Thecomposition includes saline and/or contrast agent. The particles and/orcomposition are sterilized.

Embodiments may also include one or more of the following. The gellingcompound is a polysaccharide. The gelling compound is alginate. Thealginate has a guluronic acid content of about 60% or more. The dropsare contacted with a gelling agent. The gelling agent is a divalentcation. The cation is Ca+2. The base polymer is PVA. The PVA is reactedby acetalization. The PVA has a molecular weight of about 75,000 g/moleor greater. The viscosity of the base polymer and gelling compound ismodified prior to forming said drops. The viscosity is modified byheating. The drops are formed by vibratory nebulization.

Embodiments may also include one or more of the following.Administration is by percutaneous injection. Administration is by acatheter. The particles are introduced to the body through a lumen, andthe lumen has a smaller diameter than the particles.

The particles can be tailored to a particular application by varyingparticle size, porosity gradient, compressibility, sphericity anddensity of the particles. The uniform size of the spherical particlescan, for example, fit through the aperture of a needle or a catheter foradministration by injection to a target site without partially orcompletely plugging the lumen of the needle or the catheter. Sizeuniformity of +15% of the spherical particles allows the particles tostack evenly.

Embodiments may have one or more of the following advantages. Theparticles are relatively inert and biocompatible (e.g., they do nottrigger an allergic or cytotoxic response). The particles do notsubstantially migrate, which can cause adverse effects. The particlesare relatively non-bioresorbable. As a result, the particles retaintheir efficacy, and the need for repeated procedures is reduced, whichcan lower cost, trauma, and/or complications. The particles can be usedin a variety of applications.

Other aspects, features, and advantages of the invention will beapparent from the description of the preferred embodiments thereof andfrom the claims.

DESCRIPTION OF DRAWINGS

FIGS. 1A and 1B illustrate a method of treating tissue.

FIG. 2 illustrates a method of treating tissue.

FIG. 3A is a light micrograph of a collection of hydrated particles;FIG. 3B is a scanning electron microscope (SEM) photograph of theparticle surface; and FIGS. 3C–3E are cross-sections of the particles.

FIG. 4A is a schematic of the manufacture of a composition; and FIG. 4Bis an enlarged schematic of region A in FIG. 4A.

FIG. 5 is a photograph of gel-stabilized drops.

FIG. 6 is a graph of particle size uniformity.

FIGS. 7A–7F illustrate a method of treating tissue.

DETAILED DESCRIPTION

Referring to FIGS. 1A and 1B, a method of treating tissue 20, here,located adjacent to a passageway 22, is shown. Passageway 22 is definedby a wall 24, e.g., of a urethra or a ureter. The method generallyincludes placing a composition 27 including highly water insoluble, highmolecular weight polymer particles 25 into tissue 20. Particles 25,e.g., acetalized polyvinyl alcohol, have a substantially uniform shapeand a symmetric compressibility. Particles 25 can increase bulk andlocalize compression, thereby reducing the size of passageway 22 andassisting tissue 20 in closing to reduce (e.g., minimize or eliminate)flow of matter, such as urine, through the passageway. As describedbelow, composition 27 can include other materials, such as a carrier, acontrasting agent, and/or a therapeutic agent.

As shown, the method includes injecting composition 27 into tissue 20.Before composition 27 is injected, a cytoscope 26 is introduced intopassageway 22 by conventional cytoscopic techniques. Cytoscope 26includes an elongated sheath 28 that defines a channel 30. In channel30, cytoscope 26 includes a light emitting element 32 (such as an opticfiber) and a viewing element 34. Cytoscope 26 is positioned at alocation selected to view a target area 36 to be treated.

Subsequently, a needle 38 is inserted into tissue 20 to target area 36,but without penetrating wall 24. Composition 27 including particles 25is then injected from a syringe (not shown) to area 36. The progress ofthe injection can be monitored, for example, by viewing changes, e.g.,narrowing, in passageway 22 through cytoscope 26 or by fluoroscopic orspectroscopic techniques, e.g., in embodiments in which composition 27includes a contrasting agent (described below). In other embodiments,referring to FIG. 2, needle 38 is inserted through channel 30 ofcytoscope 26 to deliver composition 27.

The methods described above can be used for a variety of medicalapplications, such as for the treatment of intrinsic sphinctericdeficiency (ISD). For example, composition 27 can be used to treaturinary incontinence. Composition 27 can be injected into the tissue ofthe urinary tract, wherein the selected site can be, for example, themucosal tissue of the bladder neck, the urethra or urethral sphincter.The resulting bulking or augmentation of the urethral tissue can reduceor restrict the size of the urethra or urinary passage and thus assistin overcoming incontinence. Methods and techniques of placing bulkingmaterials for the treatment of urinary incontinence are described inNamiki, “Application of Teflon Paste for Urinary Incontinence—Report ofTwo Cases”, Urol. Int., Vol. 39, pp. 280–282 (1984); Politano et al.,“Periurethral Teflon Injection for Urinary Incontinence”, The Journal ofUrology, Vol. 111, pp. 180–183 (1974); Winters, et al., “PeriurethralInjection of Collagen in the Treatment of Intrinsic SphinctericDeficiency in the Female Patient”, Urologic Clinics of North America,22(3):473–478 (1995); U.S. Pat. Nos. 5,007,940; 5,158,573; 5,116,387;and references cited therein.

Composition 27 can be injected into the tissue of the anal canal,wherein the selected site can be, for example, the mucosal tissue of theanal canal, such as near the internal or external anal sphincter muscle.The resulting bulking or augmentation of the tissue can restrict thesize of the sphincter or anal passage and thus assist in reducing fecalor anal incontinence. Composition 27 can also be used to treat, e.g.,repair, structurally defective and/or inadequately functioning musclesof the anal sphincter. For example, a physician can perianally injectcomposition 27 into a deformity, e.g., a keyhole deformity resultingfrom trauma or surgery, using one or more injections, until thedeformity is repaired or the treated area is restored to its properform. Methods of placing biocompatible materials to treat the sphinctermuscles are described in Freed, U.S. Pat. No. 5,490,984.

Composition 27 can be used to treat vesicoureteral reflux. For example,composition 27 can be placed in the subureteral tissue to compress theureter, thereby reducing the reflux of urine into the ureter. Methodsfor delivering a composition to treat vesicoureteral reflux aredescribed in Capozza, et al., “Endoscopic Treatment of Vesico-UretericReflux and Urinary Incontinence: Technical Problems in the PediatricPatient,” Br. J. Urol., 75: 538–542 (1995); and Smith et al.,“Evaluation of Polydimethylsiloxane as an Alternative in the EndoscopicTreatment of Vesicoureteral Reflux”, J. Urol., 152: 1221–1224, 1994.

Composition 27 can be applied to gastroesophageal reflux disease (GERD)applications. Composition 27 can be injected into the mucosal tissue ofthe upper gastrointestinal tract, wherein the selected site may be, forexample, the mucosal tissue of the cardiac orifice of the stomach, whichopens into the esophagus. The resulting bulking or augmentation of thetissue can restrict the size of the passage and thus assist in reducinggastric fluids refluxing into the esophagus. Methods and techniques aredescribed, for example, in Shafik, “Intraesophageal Polytef Injectionfor the Treatment of Reflux Esophagitis”, Surg. Endoscopy, 10:329–331(1996), and references cited therein.

Composition 27 can also be used to treat other conditions, such as vocalcord paralysis, e.g., to restore glottic competence in cases ofparalytic dysphonia. Such general treatment methods are described inHirano et al., “Transcutaneous Intrafold Injection for Unilateral VocalCord Paralysis: Functional Results”, Ann. Otol. Rhinol. Laryngol., Vol.99, pp. 598–604 (1990); Strasnick et al., “Transcutaneous Teflon®Injection for Unilateral Vocal Cord Paralysis: An Update”, Laryngoscope,Vol. 101, pp. 785–787 (July 1991); and references cited therein.

In other embodiments, composition 27 is used to treat soft tissue. Forexample, composition 27 can be used for reconstructive or cosmeticapplications, e.g., surgery. Examples of applications includereconstruction of cleft lips; scars, e.g., depressed scars from chickenpox or acne scars; indentations resulting from liposuction; wrinkles,e.g., glabella frown wrinkles; and soft tissue augmentation of thinlips. Composition 27 can be used as a graft material or a filler to filland/or to smooth out soft tissue defects. For example, composition 27can be injected percutaneously under a defect until the appearance ofthe defect, e.g., a wrinkle, is reduced. Procedures and techniques aredescribe, for example, in Ersek et al., “Bioplastique: A New TexturedCopolymer Microparticles Promises Permanence in Soft-TissueAugmentation”, Plastic and Reconstructive Surgery, Vol. 87, No. 4, pp693–702 (April 1991); Lemperle et al., “PMMA Microspheres forIntradermal Implantation: Part I. Animal Research”, Annals of PlasticSurgery, Vol. 26, No. 1, pp. 57–63 (1991); and references cited therein.

For the applications described above, the amount of composition 27delivered can vary based on the nature, location and severity of thecondition to be treated and the route of administration, the size ofparticles 25, and factors relating to the patient. A physician treatingthe condition, disease or disorder can determine an effective amount ofcomposition 27. An effective amount of composition 27 refers to theamount sufficient to result in amelioration of symptoms or aprolongation of survival of the patient.

In other embodiments, particles 25 can also be used for implantableprostheses, such as mammary or breast implants, penile implants, ortesticular prostheses. For example, particles 25 can be encased in ashell made of compliant material, such as silicone elastomers,polyolefins, polyurethanes, ethylene-propylene diene monomers, orethylene-propylene rubbers. In embodiments, particles 25 can be usedwithout a shell because they can remain at the delivery site and do notmigrate. Prostheses are described, for example, in U.S. Pat. Nos.5,941,909; 6,060,639; 5,063,914; and references cited therein.

The Composition

As described above, composition 27 includes polymer particles 25. Inembodiments, composition 27 also includes a carrier, a contrastingagent, and/or a therapeutic agent.

The particles: Particles 25 are substantially formed of polymer such asa highly water insoluble, high molecular weight polymer. As will bediscussed below, a preferred polymer is high molecular weight polyvinylalcohol (PVA) that has been acetalized. Preferably, the particles aresubstantially pure intrachain 1,3 acetalized PVA and substantially freeof animal derived residue such as collagen. In embodiments, theparticles include a minor amount, e.g. less than about 0.2 weight %, ofalginate or another polysaccharide or gelling material.

Referring to FIG. 3A, particles 111 have a substantially uniformspherical shape and size. Referring to FIG. 3B, each particle has awell-defined outer spherical surface including relatively small,randomly located pores. The surface appears substantially smooth, withsome larger surface morphology such as crevice-like features. Referringto FIGS. 3C–3E, SEM images of cross-sections through particles, the bodyof the particle defines pores which provide compressibility and otherproperties. Pores near the center of the particle are relatively largeand pores near the surface of the particle are relatively small.

The region of small pores near the periphery of the particle isrelatively stiff and incompressible, which enhances resistance to shearforces and abrasion. In addition, the variable pore size profileproduces a symmetric compressibility and, it is believed, acompressibility profile such that the particles are relatively easilycompressed from a maximum, at rest diameter to a smaller, compressedfirst diameter but compression to even smaller diameter requiressubstantially greater force. A variable compressibility profile isbelieved to be due to the presence of a relative weak, collapsibleinter-pore wall structure in the center region where the pores arelarge, and a stiffer inter-pore wall structure near the surface of theparticle, where the pores are more numerous and relatively small. Thevariable pore size profile also is believed to enhance elastic recoveryafter compression. The pore structure also influences the density of theparticles and the rate of carrier fluid or body fluid uptake.

The particles can be delivered through a needle having a lumen area thatis smaller, e.g. 50% smaller or less, than the uncompressedcross-sectional area of the particles. As a result, the particles arecompressed to pass through the needle for delivery into the body. Thecompression force is provided indirectly by increasing the pressureapplied to the carrier fluid by depressing the syringe plunger. Theparticles are relatively easily compressed to diameters sufficient fordelivery through the needle into the body. The robust, rigid surfaceregion resists abrasion when the particles contact hard surfaces such assyringe surfaces, and the needle lumen wall (e.g. stainless steel)during delivery. Once in the body, the particles substantially recoverto original diameter and shape, and form a dense mass. The compressioncan be limited by the compression profile of the particles, and thenumber of particles needed at a particular target area can be reduced.

In embodiments, the particles have a diameter of about 1500 or 1200microns or less, and about 10 microns or more, e.g. about 400 microns ormore and the pores are about 50 or 35 to 0.01 micron. The particles canbe classified in size ranges of about 500–700 microns, about 700–900microns, or about 900–1200 microns. The particles typically have a meandiameter in approximately the middle of the range and variance of about20% or less, e.g. 15% or 10% or less.

The particular size of the particles used can also be a function oftheir application. For example, for cosmetic applications, relativelysmall particles can be used to provide a more natural feel and to reducea granular texture. Small particles can also be delivered through smallneedles, which can reduce psychological trauma and discomfort to thepatient.

Referring particularly to FIG. 3C, the particles can be considered toinclude a center region, C, from the center of the particle to a radiusof about r/3, a body region, B, from about r/3 to about 2 r/3 and asurface region, S, from 2r/3 to r. The regions can be characterized bythe relative size of the pores and the number of pores of given sizes.In embodiments, the center region has a greater number of relativelylarge pores than the body region and the surface region. The large poresare in the range of about 20 micron or more, e.g. 30 micron or more, orin the range of about 20 to 35 micron. The body region has a greaternumber of intermediate size pores than the surface region. Theintermediate size pores are in the range of about 5 to 18 micron. Inembodiments, the regions may also have different densities, with thedensity of the surface region being greater than the density of the bodyregion, and the density of the body region being greater than thedensity of the center region.

The size of the pores in each of the regions can also be characterizedby a distribution. In embodiments, the predominant pore size(s) in thecenter region being greater than the predominant pore size(s) in thebody region and the predominant pore size(s) in the body region isgreater than the predominant pore size(s) in the surface region. Inembodiments, in the predominant pore size in the center region is 20micron or more, e.g. 30 microns or more, or in the range of about 20 to35 microns. The predominant pore size in the body region is about 18micron or less, e.g. about 15 micron or less, or in the range of about18 to 2 micron. The pores in the surface region are preferablypredominantly less than about 1 micron, e.g. about 0.1 to 0.01 micron.

In embodiments, the predominant pore size in the body region is about 50to 70% of the pore size in the center region and the pore size in thesurface region is about 10% or less, e.g. about 2% of the pore size inthe body region. The size of the pores on the outer surface of theparticle is predominantly in the range of about 1 micron or less, e.g.about 0.1 or 0.01 micron. In embodiments, the surface and/or surfaceregion is substantially free of pores having a diameter larger thanabout 10 micron or larger than about 1 micron. In embodiments, thepredominant pore size is in the region 0.8 or 0.9r to r is about 1micron or less, e.g. 0.5 to 0.1 micron or less. The region from thecenter of the particle to 0.8 or 0.9r has pores of about 10 micron orgreater and/or has a predominant pore size of about 2 to 35 micron. Inembodiments, the predominant pore size in the region 0.8 or 0.9r to r isabout 5% or less, e.g. 1% or 0.3% or less than the predominant pore sizein the region from the center to 0.9r. the largest pores in theparticles can have a size in the range of 1% or 5% or 10% or more of theparticle diameter.

The size of the pores can be measured by viewing a cross-section as inFIG. 3C. For irregularly shaped pores, the maximum visible cross-sectionis used. The predominant pore size(s) can be found by measuring the sizeof the visible pores and plotting the number of pores as a function ofsize. The predominant pore size(s) are the sizes that are about themaximum in the distribution. In FIG. 3C, the SEM was taken on wetparticles including absorbed saline, which were frozen in liquidnitrogen and sectioned. (FIG. 3B was taken prior to sectioning.) InFIGS. 3D and 3E, the particle was freeze-dried prior to sectioning andSEM analysis.

Referring to FIG. 4A, a system for manufacturing particles includes aflow controller 300, a drop generator 310, a gelling vessel 320, areactor vessel 330, a gel dissolution chamber 340 and a filter 350. Theflow controller 300 delivers polymer solutions to a viscosity controller305, which heats the solution to reduce viscosity prior to delivery tothe drop generator 310. The drop generator 310 forms and directs dropsinto a gelling vessel 320, where drops are stabilized by gel formation.The gel-stabilized drops are transferred from the gelling vessel 320 toreactor vessel 330 where the polymer in the gel-stabilized drops isreacted forming precursor particles. The precursor particles aretransferred to a gel dissolution chamber 340, where the gel isdissolved. The particles are then filtered in a filter 350 to removedebris, sterilized, and packaged.

A base polymer and a gelling precursor are dissolved in water and mixed.The mixture is introduced to a high pressure pumping apparatus, such asa syringe pump (e.g., model PHD4400, Harvard Apparatus, Holliston,Mass.). Examples of base polymers include polyvinyl alcohol, polyacrylicacid, polymethacrylic acid, poly vinyl sulfonate, carboxymethylcellulose, hydroxyethyl cellulose, substituted cellulose,polyacrylamide, polyethylene glycol, polyamides, polyureas,polyurethanes, polyester, polyethers, polystyrene, polysaccharide,polylactic acid, polyethylene, polymethylmethacrylate and copolymers ormixtures thereof. A preferred polymer is polyvinyl alcohol. Thepolyvinyl alcohol, in particular, is hydrolyzed in the range of 80 to99%. The weight average molecular weight of the base polymer can be inthe range of 9000 to 186,000, 85,000 to 146,000 or 89,000 to 98,000.Gelling precursors include, for example, alginates, alginate salts,xanthan gums, natural gum, agar, agarose, chitosan, carrageenan,fucoidan, furcellaran, laminaran, hypnea, eucheuma, gum arabic, gumghatti, gum karaya, gum tragacanth, hyaluronic acid, locust beam gum,arabinogalactan, pectin, amylopectin, other water solublepolysaccharides and other ionically crosslinkable polymers. A particulargelling precursor is sodium alginate. A preferred sodium alginate ishigh guluronic acid, stem-derived alginate (e.g. about 50 or 60% or moreguluronic acid with a low viscosity e.g. about 20 to 80 cps at 20° C.)which produces a high tensile, robust gel. High molecular weight PVA isdissolved in water by heating, typically above about 70° C., whilealginates can be dissolved at room temperature. The PVA can be dissolvedby mixing PVA and alginate together in a vessel which is heated toautoclave temperature (about 121° C.). Alternatively, the PVA can bedisposed in water and heated and the alginate subsequently added at roomtemperature to avoid exposing the alginate to high temperature. Heat canalso be applied by microwave application. In embodiments, forPVA/alginate, the mixture is typically about 7.5 to 8.5%, e.g. about 8%by weight PVA and about 1.5 to 2.5%, e.g. about 2%, by weight alginate.

Referring to FIG. 4B, the viscosity controller 305 is a heat exchangercirculating water at a predetermined temperature about the flow tubingbetween the pump and drop generator. The mixture of base polymer andgelling precursor flows into the viscosity controller 305, where themixture is heated so that its viscosity is lowered to a level forefficient formation of very small drops. For a high molecular weightPVA/alginate solution, the temperature of the circulating water is lessthan about 75° C. and more than about 60° C., for example, 65° C. whichmaintains the mixture at a viscosity of 90–200 centipoise. For sphericalparticles, the viscosity of the drops is maintained so they are capturedin the gelling vessel without splintering or cojoining which can createirregular, fiberous particles. In other embodiments, the flow controllerand/or the drop generator can be placed in a temperature-controlledchamber, e.g. an oven, or a heat tape wrap, to maintain a desiredviscosity.

The drop generator 310 generates substantially spherical drops ofpredetermined diameter by forcing a stream of the mixture of basepolymer and gelling precursor through a nozzle which is subject to aperiodic disturbance to break up the jet stream into drops. The jetstream can be broken into drops by vibratory action generated forexample, by an electrostatic or piezoelectric element. The drop size iscontrolled by controlling the flow rate, viscosity, amplitude, andfrequency at which the element is driven. Lower flow rates and higherfrequencies produce smaller drops. A suitable electrostatic dropgenerator is available from NISCO Engineering, model NISCO Encapsulationunit VAR D, Zurich, Switzerland. In embodiments, the frequency is in therange of about 0.1 to 0.8 kHz. The flow rate through the dropletgenerator is in the range of about 1 to 12 mL per minute. The dropgenerator can include charging the drops after formation such thatmutual repulsion between drops prevents drop aggregation as drops travelfrom the generator to the gelling vessels. Charging may be achieved by,e.g. an electrostatic charging device such as a charged ring positioneddownstream of the nozzle.

Drops of the base polymer and gelling precursor mixture are captured inthe gelling vessel 320. The gelling vessel 320 contains a gelling agentwhich interacts with the gelling precursor to stabilize drops by forminga stable gel. Suitable gelling agents include, for example, a divalentcation such as alkali metal salt, alkaline earth metal salt or atransition metal salt that can ionically crosslink with the gellingagent. An inorganic salt, for example, a calcium, barium, zinc ormagnesium salt can be used as a gelling agent. In embodiments,particularly those using an alginate gelling precursor, a suitablegelling agent is calcium chloride. The calcium cations have an affinityfor carboxylic groups in the gelling precursor. The cations complex withcarboxylic groups in the gelling precursor resulting in encapsulation ofthe base polymer in a matrix of gelling precursor.

Referring to FIG. 5, a photo-image of the gelled particles, the gellingagent is in an amount selected in accordance with the desired propertiesof the particles. As evident, a pore structure in the particle forms inthe gelling stage. The concentration of the gelling agent can controlpore formation in the particle, thereby controlling the porositygradient in the particle. Adding non-gelling ions, for example, sodiumions, to the gelling solution can reduce the porosity gradient,resulting in a more uniform intermediate porosity throughout theparticle. In embodiments, the gelling agent is, for example, 0.01–10weight percent, 1–5 weight percent or 2 weight percent in deionizedwater. In embodiments, particles, including gelling agent and a porestructure can be used in composition 27.

Following drop stabilization, the gelling solution is decanted from thesolid drops and the stabilized drops are transferred to the reactorvessel 330. In the reactor vessel 330, the stabilized drops are reactedto produce precursor particles. The reactor vessel includes an agentthat chemically reacts with the base polymer, e.g. to cause crosslinkingbetween polymer chains and/or within a polymer chain. The agent diffusesinto the stabilized drops from the surface of the particle in a gradientwhich, it is believed, provides more crosslinking near the surface ofthe stabilized drop compared to the body and center of the drop.Reaction is greatest at the surface of the drop, providing a stiff,abrasion resistant exterior. For polyvinyl alcohol, for example, thevessel 330 includes aldehydes, such as formaldehyde, glyoxal,benzaldehyde, aterephthalaldehyde, succinaldehyde and glutaraldehyde forthe acetalization of polyvinyl alcohol. The vessel 330 also includes anacid, for example, strong acids such as sulfuric acid, hydrochloricacid, nitric acid and weak acids such as acetic acid, formic acid andphosphoric acid. In embodiments, the reaction is primarily a 1,3acetalization:

This intra-chain acetalization reaction can be carried out withrelatively low probability of inter-chain crosslinking as described inJohn G. Pritchard “Poly(Vinyl Alcohol) Basic Properties And Uses(Polymer Monograph, vol. 4) (see p. 93–97), Gordon and Breach, SciencePublishers LTD., London, 1970, the entire contents of which is herebyincorporated by reference. Some OH groups along a polymer chain canremain unconverted since the reaction proceeds in a random fashion andthere can be left over OH groups that do not react with adjacent groups.

Adjusting the amount of aldehyde and acid used, reaction time andreaction temperature can control the degree of acetalization. Inembodiments, the reaction time is e.g., 5 minutes to 1 hour, 10 to 40minutes or 20 minutes. The reaction temperature can be 25° C. to 150° C.or 75° C. to 130° C. or 65° C. The reactor vessel is placed in a waterbath fitted with an orbital motion mixer. The crosslinked precursorparticles are washed several times with deionized water to neutralizethe particles and remove any residual acidic solution.

The precursor particles are transferred to the dissolution chamber 340to remove the gelling precursor, e.g. by an ion exchange reaction. Inembodiments, sodium alginate is removed by ion exchange with a solutionof sodium hexa-metaphosphate (EM Science). The solution can include, forexample, ethylenediaminetetraacetic acid (EDTA), citric acid, otheracids and phosphates. The concentration of the sodium hexa-metaphosphatecan be, for example, 1–20 weight %, 1–10 weight % or 5 weight % indeionized water. Residual gelling precursor, for example, sodiumalginate, can be determined by assay for detection of uronic acids in,for example, alginates containing mannuronic and guluronic acidresidues. Suitable assays include rinsing the particles with sodiumtetraborate in sulfuric acid solution to extract alginate and combiningthe extract with metahydroxydiphenyl colormetric reagent and determiningconcentration by UV/VIS spectroscopy. Testing can be carried out byalginate suppliers such as FMC Biopolymer, Oslo, Norway. Residualalginate can be present in the range of about 20–35% by weight prior torinsing and in the range of about 0.01–0.5% or 0.1–0.3% or 0.18% in theparticles after rinsing for 30 minutes in water at about 23° C.

The particles are filtered through filter 350 to remove residual debris.Particles of 500 to 700 microns are filtered through a sieve of 710microns and then a sieve of 300 microns. Particles of 700 to 900 micronsare filtered through a sieve of 1000 microns and then a sieve of 500microns. Particles of 900 to 1200 microns are filtered through a sieveof 1180 microns and then a sieve of 710 microns.

The filtered particles are sterilized by a low temperature techniquesuch as e-beam irradiation, and packaged. In embodiments, electron beamirradiation can be used to pharmaceutically sterilize the particles toreduce bioburden. In e-beam sterilization, an electron beam isaccelerated using magnetic and electric fields, and focused into a beamof energy. This resultant beam can be scanned by means of anelectromagnet to produce a “curtain” of accelerated electrons. Theaccelerated electron beam penetrates the collection of particles toconfer upon them electrons which destroy bacteria and mold to sterilizeand reduce the bioburden in the particles. Electron beam sterilizationcan be performed by sterilization vendors, such as Titan Scan, Lima,Ohio.

Additional information about the particles is described in commonlyassigned U.S. Ser. No.10/215,594, filed Aug. 9, 2002, and entitled“Embolization”, hereby incorporated by reference in its entirety.

The following example is illustrative and not intended to be limiting.

EXAMPLE

Particles are manufactured from an aqueous solution containing 8 weight% of polyvinyl alcohol, 99+% hydrolyzed, average M_(w) 89,000–120,000(ALDRICH) and 2 weight % of gelling precursor, sodium alginate, PRONOVAUPLVG, (FMC BioPolymer, Princeton, N.J.) in deionized water and themixture is heated to about 121° C. The solution has a viscosity of about310 centipoise at room temperature and a viscosity of about 160 cps at65° C. Using a syringe pump (Harvard Apparatus), the mixture is fed todrop generator (Nisco Engineering). Drops are directed into a gellingvessel containing 2 weight % of calcium chloride in deionized water andstirred with a stirring bar. The calcium chloride solution is decantedwithin about three minutes to avoid substantial leaching of thepolyvinyl alcohol from the drops into the solution. The drops are addedto the reaction vessel containing a solution of 4% by weight offormaldehyde (37 wt % in methanol) and 20% by weight sulfuric acid(95–98% concentrated). The reaction solution is stirred at 65° C. for 20minutes. Precursor particles are rinsed with deionized water (3×300 mL)to remove residual acidic solution. The sodium alginate is substantiallyremoved by soaking the precursor particles in a solution of 5 weight %of sodium hexa-methaphosphate in deionized water for 0.5 hour. Thesolution is rinsed in deionized water to remove residual phosphate andalginate. The particles are filtered by sieving, as discussed above,placed in saline (USP 0.9% NaCl) and followed by irradiationsterilization.

Particles were produced at the nozzle diameters, nozzle frequencies andflow rates (amplitude about 80% of maximum) described in Table 1.

TABLE 1 Nozzle Suspend- Bead Size Diameter Frequency Flow Rate Densityability (microns) (microns) (kHz) (mL/min) (g/mL) Sphericity (minutes)500–700  150 0.45 4 — 0.92 3 700–900  200 0.21 5 1.265 0.94 5 900–1200300 0.22 10 — 0.95 6

Suspendability is measured at room temperature by mixing a solution of 2ml of particles in 5 ml saline with contrast solution (Omnipaque 300,Nycomed, Buckinghamshire, UK) and observing the time for about 50% ofthe particles to enter suspension, i.e. have not sunk to the bottom orfloated to the top of a container (about 10 ml, 25 mm diameter vial).Suspendability provides a practical measure of how long the particleswill remain suspended. (Omnipaque is an aqueous solution of Iohexol,N.N.-Bis(2,3-dihydroxypropyl)-T-[N-(2,3-dihydroxypropyl)-acetamide]-2,4,6-trilodo-isophthalamide;Omnipaque 300 contains 647 mg of iohexol equivalent to 300 mg of organiciodine per ml. The specific gravity of 1.349 of 37° C. and an absoluteviscosity 11.8 cp at 20° C.) The particles remain in suspension forabout 2 to 3 minutes.

Particle size uniformity and sphericity is measured using a BeckmanCoulter RapidVUE Image Analyzer version 2.06 (Beckman Coulter, Miami,Fla.). Briefly, the RapidVUE takes an image of continuous-tone(gray-scale) form and converts it to a digital form through the processof sampling and quantization. The system software identifies andmeasures particles in an image in the form of a fiber, rod or sphere.Sphericity computation and other statistical definitions are in AppendixA, attached, which is a page from the RapidVUE operating manual.

Referring to FIG. 6, particle size uniformity is illustrated forparticles 700–900 micron. The x-axis is the particle diameter. They-axis is the volume normalized percentage of particles at each particlesize. The total volume of particles detected is computed and the volumeof the particles at each diameter is divided by the total volume. Theparticles have distribution of particle sizes with variance of less thanabout ±15%.

While substantially spherical particles are preferred, non-sphericalparticles can be manufactured and formed by controlling, e.g., dropformation conditions or by post-processing the particles, e.g. bycutting or dicing into other shapes. Particles can also be shaped byphysical deformation followed by crosslinking. Particle shaping isdescribed in U.S. Ser. No. 10/116,330, filed Apr. 4, 2002.

Carrier: Composition 27 can include one or more carrier materials thatallow the composition to be delivered in a first state, e.g., arelatively fluid or low viscosity state, and change, e.g., by phasetransition, to a second state, e.g., a relatively high viscosity orrigid state. In embodiments, particles 25 can be suspended in abiocompatible, resorbable lubricant, such as a cellulose polysaccharidegel having water, glycerin and sodium carboxymethylcellulose. The gelenables particles 25 to remain in suspension without settling. Otherpolysaccharides can also be included such as cellulose, agarmethylcellulose, hydroxypropyl methylcellulose, ethylcellulose,microcrystalline cellulose, oxidized cellulose, and other equivalentmaterials.

The polysaccharide gel is biocompatible, and the lubricious nature ofthe polysaccharide gel can reduce the frictional forces generated duringthe transferring of the particles from a syringe by injection into thetissue site. In addition, polysaccharides do not generate an antigenicresponse, and the polysaccharide gel is readily sterilizable and stableat ambient conditions and does not need refrigeration for storage andshipment.

After injection of composition 27 into the tissue, the polysaccharidegel can be resorbed by the tissue, leaving the non-resorbable matrix ofparticles 25 in place in the particular area or bolus, where it canremain without migrating to other areas of the body.

Other examples of carriers include undiluted agarose, methyl celluloseor other linear unbranched polysaccharide, dextran sulfate, succinylatednon-crosslinked collagen, methylated non-crosslinked collagen, glycogen,dextrose, maltose, triglycerides of fatty acids, egg yolk phospholipids,heparin, DMSO, phosphate buffered saline, and the like. Examples ofcollagen are described in U.S. Pat. No. 5,490,984. More examples ofappropriate carriers include hyaluronic acid, polyvinyl pyrrolidone or ahydrogel derived thereof, dextran or a hydrogel derivative thereof,glycerol, polyethylene glycol, succinylated collagen, liquid collagen,oil based emulsions such as corn oil or safflower, B-D glucose (orB-glucan, as described in U.S. Pat. No. 6,277,392) or otherpolysachaarides or biocompatible organic polymers either singly or incombination with one or more of the above materials.

Hydrogel compositions, such as those that swell upon injection intotissue due to hydration by physicologic fluid, are described, forexample, in U.S. Pat. Nos. 6,423,332; 6,306,418; and 5,902,832. Inembodiments, the composition can swell from an initial dehydrated volumeto a final hydrated volume that is substantially the same as the initialtotal volume of composition injected into the tissue to be treated.Examples include poly(ethylene oxide), polyvinyl pyrrolidone, polyvinylalcohol, poly(propylene oxide), poly(ethylene, glycol), poly(propyleneglycol), polytetramethylene oxide, polyacrylamide, poly(hydroxy ethylacrylate), poly(hydroxy ethyl methacrylate), hydroxy ethyl cellulose,hydroxy propyl cellulose, methoxylated pectin gels, agar, a starch suchas cornstarch, a modified starch, an alginate, a hydroxy ethylcarbohydrate, or the like and should preferably be adjusted so as toallow swelling to a selected percent after hydration. The carrier candisperse over time.

In some embodiments, composition 27 includes between about 0.5 to about50 weight percent of the carrier. For example, composition 27 caninclude greater than or equal to about 0.5, 5, 10, 15, 20, 25, 30, 35,40, or 45 weight percent of the carrier; and/or less than or equal toabout 50, 45, 40, 35, 30, 25, 20, 15, 10, or 5 weight percent of thecarrier.

Contrasting agent: In embodiments, composition 27 includes a contrastingagent. The contrast agent can be a biocompatible material capable ofbeing monitored during injection by, for example, radiography,fluoroscopy, ultrasound, or visually. The contrast agent can be watersoluble or water insoluble. Examples of water soluble contrast agentsinclude metrizamide, iopamidol, iothalamate sodium, iodomide sodium, andmeglumine. Examples of water insoluble contrast agents include tantalum,tantalum oxide, and barium sulfate, each of which is available in a formfor in vivo use including a particle size of about 10 microns or less.Other water insoluble contrast agents include gold, tungsten, andplatinum powders.

Some examples of radiopaque materials include paramagnetic materials(e.g. persistent free radicals) and compounds, salts, and complexes ofparamagnetic metal species (e.g., transition metal or lanthanide ions);heavy atom (e.g., atomic number of 37 or more) compounds, salts, orcomplexes (e.g., heavy metal compounds, iodinated compounds, etc.);radionuclide-containing compounds, salts, or complexes (e.g. salts,compounds or complexes of radioactive metal isotopes or radiodinatedorganic compounds); and superparamagentic materials (e.g., metal oxideor mixed oxide particles, particularly iron oxides). Paramagnetic metalsinclude Gd (III), Dy (III), Fe (III), Fe (III), Mn (III) and Ho (III),and paramagnetic Ni, Co and Eu species. Heavy metals include Pb, Ba, Ag,Au, W, Cu, Bi and lanthanides such as Gd. Metals, metal oxides, andalloys, including but not limited to medical grade stainless steel,silver, gold, titanium and titanium alloys, oxide derivatives ofstainless steel or titanium or titanium alloys, aluminum oxide, andzirconium oxide can also be used. The amount of contrasting agent usedcan be any amount sufficient to be detected.

Therapeutic agent: In embodiments, particles 25 include one or moretherapeutic agents. For example, an effective amount of wound healingagents can be added to composition 27. These agents include proteingrowth factors such as fibroblast growth factors (FGFs), plateletderived growth factors (PDGFs), epidermal growth factors (EGFs),connective tissue activated peptides (CTAPs), transforming growthfactors (TGFs), and the like. The amount of wound healing agent(s) to beincluded with composition 27 can vary, depending, for example, on thepatient (age, sex, medical history) and the site being treated. Inembodiments, composition 27 includes antimicrobial additives and/orantibodies to reduce the potential for infection at the treatment site.Other agents are described in commonly assigned U.S. Ser. No.10/232,265,filed on Aug. 30, 2002, and entitled “Drug Delivery Particles”. Thetherapeutic agent can be added to composition 27 and/or be placed onparticles 25.

Other additives: Composition 27 can include one or more materials thatenhance the mechanical and/or physical properties of the composition. Insome embodiments, particles 25 can be combined with one or morerelatively hard materials. The relatively hard material can be, forexample, biocompatible ceramics, biocompatible metals (e.g., stainlesssteel), glass, or other biocompatible materials such as calcium salts,e.g., hydroxyapatite. The combination of particles 25 and hardmaterial(s) can be used, for example, to fill depressed scars,unsymmetrical orbital floors, or bone defects in reconstructive surgicalprocedures.

Other methods can be used to placed particles 25 and/or composition 27into tissue. For example, particles 25 and/or composition 27 can beplaced laproscopically. Particles 25 and/or composition 27 can also beplaced in a cavity or void created in tissue.

Referring to FIGS. 7A–7F, a method of placing particles 25 and/orcomposition 27 is shown. The method includes using a catheter or asheath 402, e.g., a blunt-ended hypotube, configured to proximallyreceive a penetration device 404, e.g., one having a trocar at itsdistal end. Penetration device 404 is inserted into sheath 402 to allowthe sheath to penetrate into tissue 403 (FIG. 7A). In embodiments, thepenetration depth can be determined by striping 406 formed on sheath402. For example, the tip of penetration device 404 can penetrate about2–2.5 cm into tissue 403, while the tip of sheath 402 can penetrateabout 0.5–1 cm into the tissue. After penetration of tissue 403,penetration device 404 is withdrawn from sheath 402, which is retainedpenetrated in the tissue (FIG. 7B).

A catheter 406 carrying an uninflated balloon 408 at the distal end isthen inserted into sheath 402 (FIG. 7C) such that the balloon extendsinto tissue 403. Balloon 408 is then inflated using an inflation device,such as a syringe 410 containing saline (FIG. 7D). As balloon 408inflates, it creates a cavity or a void 412 in tissue 403. Inembodiments, balloon 408 is shaped to provide a cavity with apredetermined shape. Balloon 408 is then deflated, and catheter 406 iswithdrawn from sheath 402 (FIG. 7E). An injection device 414, such as asyringe 416 containing particles 25 and/or composition 27, is theninserted into sheath 402, and the particles and/or composition can bedelivered to cavity 412 (FIG. 7F).

In other embodiments, particles 25 and/or composition 27 can be usedwith a device, such as an indwelling sling, used to treat urinaryincontinence. An example of a device is described in WO 00/74633.Particles 25 and/or composition 27 can be placed, e.g., injected, intothe device as a bulking agent to provide lift, thereby providing anothermethod of adjusting the degree of support provided by the device.

All publications, references, applications, and patents referred toherein are incorporated by reference in their entirety.

Other embodiments are within the claims.

1. A method of treating tissue, the method comprising: placing aplurality of substantially spherical polymer particles in the tissue,wherein: the particles comprise first pores and second pores that aresmaller than the first pores; each particle has a center, a surface, aradius, a center region, and a surface region; the center region extendsradially from the center to about ⅓ of the radius; the surface regionextends radially from ⅔ of the radius to the surface; and the surfaceregion comprises fewer of the first pores than the center region.
 2. Themethod of claim 1, wherein the particles are injected into the tissue.3. The method of claim 2, wherein the particles are injectedpercutaneously.
 4. The method of claim 1, wherein the particles aredelivered through a catheter.
 5. The method of claim 1, comprisingforming a cavity in the tissue, and placing the particles in the cavity.6. The method of claim 1, wherein the tissue is adjacent to a bodypassageway.
 7. The method of claim 6, wherein the passageway is definedby a ureter.
 8. The method of claim 1, wherein the tissue is adjacent toa body passageway, the particles being placed in an amount effective tonarrow the passageway.
 9. The method of claim 1, wherein the particlescomprise polyvinyl alcohol.
 10. The method of claim 9, wherein thepolyvinyl alcohol is 1,3 diol acetalized.
 11. The method of claim 9,wherein the particles comprise a polysaccharide.
 12. The method of claim9, wherein the polysaccharide comprises alginate.
 13. The method ofclaim 1, wherein the particles comprise a therapeutic agent.
 14. Themethod of claim 1, wherein, for at least some of the plurality ofparticles, each particle has a different radius.
 15. A method oftreating an individual, the method comprising: placing a therapeuticallyeffective amount of substantially spherical particles comprisingpolyvinyl alcohol in a tissue of the individual, wherein; the particlescomprise first pores and second pores that are smaller than the firstpores; each particle has a center, a surface, a radius, a center region,and a surface region; the center region extends radially from the centerto about ⅓ of the radius; the surface region extends radially from ⅔ ofthe radius to the surface; and the surface region comprises fewer of thefirst pores than the center region.
 16. The method of claim 15, furthercomprising selecting the individual diagnosed with gastroesophagealreflux disease.
 17. The method of claim 16, wherein the tissue isadjacent to a gastrointestinal tract.
 18. The method of claim 15,further comprising selecting the individual diagnosed withvesicoureteral reflux.
 19. The method of claim 18, wherein the tissue isadjacent to a ureter.
 20. The method of claim 15, further comprisingselecting the individual diagnosed with urinary incontinence.
 21. Themethod of claim 15, further comprising selecting the individualdiagnosed with fecal incontinence.
 22. The method of claim 15, whereinthe particles are placed percutaneously.
 23. The method of claim 15,wherein the particles are placed through a catheter.
 24. The method ofclaim 15, further comprising selecting the individual diagnosed withinstrinsic sphincteric deficiency.
 25. The method of claim 15, furthercomprising selecting the individual diagnosed with vocal cord paralysis.26. The method of claim 15, further comprising selecting the individualin need of a reconstructive or cosmetic procedure.
 27. The method ofclaim 15, wherein, for at least some of the therapeutically effectiveamount of particles, each particle has a different radius.